Transcript Understanding Networking

Understanding
Networking
Joe Cicero
Northeast Wisconsin Technical College
Presentation Purpose
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The purpose of this presentation is to
give the learner a VERY BASIC
understanding of TCP /IP networking.
What we will cover…
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The NIC or Network Interface Card
TCP/IP or Transmission Control Protocol Internet Protocol
IP or Internet Protocol Addressing
What a Gateway is
Internet Addresses vs. Private IP Addresses
NAT or Network Address Translation
DNS or Domain Name Service
DHCP or Dynamic Host Configuration Protocol vs. Static
Addressing
Special IP Addresses – 169, 127
Cross-over cables
Hubs
Switches
Wireless
Ad hoc vs. Infrastructure
The Network Interface Card
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Since most of us have a phone, we will
use it to describe what is needed and how
things work on a network.
The network interface card or NIC is like
your phone. Your phone allows you to
connect to the telephone network.
The NIC is the physical device that
enables the computer to connect to a
computer network.
Language / Protocol
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We all speak some language to
communicate with someone on the other
end of our phone. If we call someone who
doesn’t speak our language and we don’t
speak their language it is impossible to
communicate with them.
One “language”, we call it a protocol, our
computer uses to “speak” to other
computers is Transmission Control
Protocol Internet Protocol or TCP IP.
The IP address
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You have a phone number. You are the only one
with this number. If two individuals had the
same phone number the system wouldn’t work
correctly. Would a caller get a busy signal if only
one of the numbers was in use? Would both
phones ring if neither was in use or would
neither?
Each computer connected to a network has an
Internet Protocol (IP) address. There can be only
one address per computer on the network. If
more than one computer has the same address
the computer turned on first will “answer calls”
for that IP and the other will not.
To view your active IP Addressing information on a
Windows computer you should always type “ipconfig /all”
at the command prompt!
NOTE: Viewing it in the Internet Protocol (TCP/IP)
Properties box DOES NOT GUARANTEE an active IP!
Gateways
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You don’t have to dial an area code when you call
someone in your area, your phone can directly
communicate with other phones in your area. If
you want to dial outside of your area you have to
dial in an area code or country code etc.
Computers on the same network can
communicate directly with other computers on
their network. If computers need to communicate
with a computer outside of the network they use
a gateway. The gateway is “aware” of other
networks and “routes” the traffic to them.
How many IP addresses are there?
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Just like there is a limited number of phone
numbers, there is a limited number of IP
addresses.
Most computers currently are using IP version 4
(IPv4) which only has 4,294,967,296 possible
unique addresses. However, many are reserved
for special purposes, such as private networks
(~18 million addresses). This reduces the
number of addresses that can be allocated as
public Internet addresses.
THERE EVENTUALLY WILL BE A SHORTAGE OF
IPv4 ADDRESSES
Internet
vs.
Private Network Addresses
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As the previous slide said there are
private addresses that you can use
on private networks (NOT THE
INTERNET). These addresses will
work on your network but won’t work
on the Internet.
They are:
• 10.0.0.0 – 10.255.255.255
16,777,216
A
• 172.16.0.0 – 172.31.255.255
1,048,57
• 169.254.0.0 – 169.254.255.255
65,536
• 192.168.0.0 – 192.168.255.255
65,536
single class
class B
class B
class C
What do/did we do about the
shortage?
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NAT or Network Address Translation was the
“patch” for the shortage. Every device on the
Internet has to have an individual address.
Every device on your network has to have an
individual address.
If you have a device BETWEEN your network and
the Internet that understands how to
communicate with your network and has a valid
Internet address, every computer doesn’t need a
valid Internet address. If you think about it, just
at NWTC, that saves thousands of IP addresses.
One device, multiple purposes
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Sometimes your NAT device is also
your gateway, router, firewall, etc.
IP Address / Domain Name
Relationship
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So we know that every computer on the
Internet has to have an address that is
unique. Why can I type a name in
Internet Explorer to get to a website?
Humans would have a hard time
remembering tons of numbers so there is
this great thing called a domain name
server that associates numbers like
72.14.203.99 with names like
www.google.com. Type either one into
your browser and you will go to the same
place.
DNS – Domain Name Server
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If you type the Preferred DNS server
number incorrectly you will NOT be
able to use a Domain name but you
will still be able to use an IP address!
DHCP vs. Static Addresses
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OK, OK, The phone company gives
me my phone number, and I’ve
never had to type any numbers into
my computer and it works – what’s
the deal?
There is this thing called DHCP or
Dynamic Host Configuration Protocol.
If your computer is setup to use it
AND there is another computer setup
to give out addresses, you don’t
have to do anything.
Statically Assigned Address
No DHCP, No Static, and I still have an
address!
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Joe, you must be wrong. I have a computer that
isn’t connected to a network and therefore can’t
be getting an address from a DHCP server, I
didn’t set an address and yet…by magic, it has an
address!
When your Windows-based computer (configured
for DHCP) is initializing, it broadcasts three or
more "discover" messages. If a DHCP server does
not respond after several discover messages are
broadcast, the Windows computer assigns itself a
Class B 169.254.0.0 address.
Who is 127.0.0.1?
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At home I’m on a 192.168.1.0 network. I
disconnected my router and pinged
127.0.0.1 and got a response! Is there an
invisible computer on my network?
127.0.0.1 is the standard IP address used
for a loopback network connection. This
means that if you try to connect to
127.0.0.1, you are immediately looped
back to your own machine.
In other words, 127.0.0.1 is you!
Other Special IP Addresses
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An IP Address that ends in a zero
denotes the “network”. You cannot
assign a computer to the address
xxx.yyy.zzz.0
Typically an IP Address that ends in
255 denotes the “broadcast”
address. You should not assign a
computer xxx.yyy.zzz.255
Cross-over cables
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Your phone at home may have a “phone cord”
just like a computer using a wired network has a
data cable. Sometimes these are referred to as a
drop cord or patch cord.
The computer sends data on some of the wires
and receives data on some of the wires.
In order to connect two computers directly
together (no other equipment in-between them),
you need a “cross-over” cable. This cable
switches the wires on the end of the cables
allowing to computers to communicate.
Hubs
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Another way for you to connect two or
more computers together is through a
“hub”.
When a “packet” of information is sent to
a hub it retransmits the “packet” to ALL
computers connected to it. Only the
computer that is at the correct address
answers. Hubs are not used much
anymore because of the increased “traffic”
on the network due to the way they work!
Switches
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Another way for you to connect two or
more computers together is through a
“switch”.
A switch keeps track of every computer
connected to it and where it is plugged
into on the switch. When a “packet” of
information is sent to a switch, it
retransmits the “packet” to the computer
the “packet” is for. Switches were more
expensive than hubs but are cheap now
and are used more often due to the way
they work!
Wireless Networking
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You may have a cordless phone or a
cell phone that uses radio waves to
communicate with other phones.
We can use radio waves with
computers too. This is called
wireless networking.
Ad hoc vs. Infrastructure
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Just like we need to have a special cable
made to make two computers
communicate without a hub or switch, we
may need to make special setting changes
to make two or more computers
communicate without an access point.